Thabeet did not begin to play basketball until the age of 15, when he began to watch pick-up games in Tanzania. When first recruited from Tanzania, Thabeet was fluent in Swahili but knew little English.[2]

As a freshman for the Connecticut Huskies, he averaged 6.2 points and 3.8 blocks per game.[3] On 3 December 2006, Thabeet tied a UConn record for blocks in a game with 10.[4] Thabeet was named to the 2007 All-Big East Rookie Team, along with teammate Jerome Dyson.

As a sophomore, he saw increased minutes and he averaged 10.5 points, 7.9 rebounds, 4.5 blocks on the season.[3] On 5 January 2008, he tied his career high in blocks with 10 in the Huskies' 73–67 loss at University of Notre Dame.[5] Thabeet was named Big East Defensive Player of the Year and to the All-Big East second team.

As a junior, Thabeet emerged on the national scene, averaging 13.6 points and 10.8 rebounds. He earned his first career triple-double against Providence College on 31 January 2009, with 15 points, 11 rebounds and 10 blocks.[6] He finished with 152 blocks on the season. He was named Big East Defensive Player of the Year and was co-Big East Player of the Year with Pitt's DeJuan Blair.[7] He was named second team All-America and National Defensive Player of the Year.

Thabeet surpassed the 1,000-point mark against Purdue on 26 March 2009. He was the third UConn player that season to do so (Jerome Dyson and A. J. Price were the others). Thabeet helped lead UConn to their first Final Four appearance since 2004.

In April 2009, Thabeet declared for the NBA draft, foregoing his final year of college eligibility.

Thabeet was selected with the second overall pick in 2009 NBA draft by the Memphis Grizzlies, becoming the first Tanzanian-born NBA player. On 13 December 2009, he had a season-high five blocks.[8]

On 25 February 2010, he was assigned to the Dakota Wizards of the NBA Development League,[9] becoming the highest ever drafted player to be sent to the D-League. On 8 March 2010, he was recalled by the Grizzlies.[10]

On 24 February 2011, Thabeet was traded, along with a future first round pick, to the Houston Rockets in exchange for Shane Battier and Ish Smith.[11] On 21 March 2011, he was assigned with the Rio Grande Valley Vipers. On 11 April 2011, he was recalled by the Rockets.

On 11 July 2012, Thabeet signed with the Oklahoma City Thunder.[13] On 26 November 2012, in a 114–69 win over the Charlotte Bobcats, Thabeet recorded his first career double-double with 13 points (a career high) and 10 rebounds.[14]

On August 26, 2014, Thabeet was traded to the Philadelphia 76ers in exchange for a trade exception and a 2015 protected second round draft pick.[15][16] On September 1, 2014, he was waived by the 76ers.[17]